George Abdaladze, Associated Press
A wounded woman lies in front of an apartment building damaged by a Russian airstrike in Gori Saturday. Russia sent tanks and troops and bombed Georgian towns in a major escalation of the conflict.

MOSCOW — Russian troops poured into Georgia Saturday as fighter jets unleashed bombs across the country, ratcheting up fears that a war has begun on Europe's border.

Russian airborne troops reached Tskhinvali, the capital of the breakaway Georgian territory of South Ossetia, where fierce fighting was reported and both sides claimed to have "liberated" the city. Russian state media reported some 100 military transport flights were planned to bring more units to the fray.

Earlier in the day, Russia Foreign Minister Sergei Lavrov said that about 1,500 people had been killed in the fighting.

The Russian ambassador to Georgia, Vyacheslav Kovalenko, upped that figure to 2,000, according to Interfax, a state newswire. Those figures could not be confirmed and were considerably higher than estimates by Georgia's government.

Georgian soldiers had tried to seize Tskhinvali, in north Georgia, on late Thursday and Friday to end the long-standing conflict between the country's government in Tblisi and the breakaway region. Russia, which backs the South Ossetians, scrambled troops in response.

On Saturday, the Georgian government said it was in a state of war and declared martial law.

At least 15 Russian peacekeepers had been killed and some 150 injured, according to Russian authorities. The Russian military confirmed to state media that two of its planes had been shot down over Georgia; Georgian officials asserted the real number was between five and 10.

Complicating the situation, a separate set of Russian-backed separatists from the area of Abkhazia, in Georgia's west, launched rocket strikes at Georgian military targets, an unnamed Abkhaz military source told Interfax.

"The situation continues to deteriorate," Lavrov said, accusing Georgia of razing whole villages in what he said amounted to "ethnic cleansing."

The rhetoric against Georgia has increasingly shifted from South Ossetian officials to the Kremlin, signaling that the battle was taking on far larger proportions.

During the past week, 34,000 refugees have fled to Russia from South Ossetia, Russian Prime Minister Vladimir Putin said at a press conference Saturday in Vladikavkaz, which is in North Ossetia just over the Russian border from South Ossetia.

The fact that Putin made a surprise visit there from Beijing, where he had been attending the Olympic Games the day before, underscored how seriously Russia is taking the matter. Putin is widely viewed as the heavier hand of the government, a man more suited than President Dmitry Medvedev at delivering a crushing blow.

Georgian officials said the fighting was the result of aggression by Russian forces and their proxies in South Ossetia, which declared independence in the early 1990s and is home to a large number of Russian citizens.

Western officials have expressed alarm at the violence, with fears growing that an all-out war between Russia and Georgia could drag in other nations, and force the United States to decide how much support to give Georgia, an ally in the region.

About 130 U.S. soldiers are in Georgia as part of ongoing efforts to help train units there, according to the Pentagon.

In Beijing, President Bush said the fighting was "a dangerous escalation" and pointedly called for Russia to end its bombings and support peace efforts launched by Europe and the United States.

"Georgia is a sovereign nation and its territorial integrity must be respected," Bush said. "We have urged an immediate halt to the violence and a stand-down by all troops."

Saakashvili, who is close to the Bush administration, accused the Russians of a widespread bombing campaign that has included towns, military bases and a seaport far outside of South Ossetia. Among the towns was Gori, between Tbilisi and South Ossetia, where a Russian bombing run reportedly hit residential apartments and killed dozens footage from the scene showed dead bodies, bloody and twisted, sprawled across the ground.

Asked about Russian airstrikes in the conversation with reporters, Lavrov said "I'm not here to justify anything" and added that any sites in the country that were connected with attacks on Russia's military or civilian populations are "not safe and they should know this."

It was not clear how far the two sides were willing to go with the fight and it was equally as unclear how they might draw back.

The Russians are publicly saying that their forces on the ground are part of a peacekeeping mission, aimed at maintaining the boundaries of South Ossetia, which is just south of the Russian border. In order for the fighting to stop, they say, Georgia must withdraw its troops from the area and sign a binding non-aggression pact—steps that seemed unlikely.

The Georgians assert that Russia has violated their sovereignty by sending in troops to augment the small peacekeeping units, essentially invading their country in an act of war, and called for the soldiers to leave immediately—which also seemed unlikely to happen soon.

Georgian officials say the Kremlin has for years deliberately set conditions in both South Ossetia and Abkhazia, funding the rebel governments and giving Russian passports to residents there, which it knew would lead to an eventual incursion.

The conflict is rooted in sharp geopolitical tensions between Russia and the West.

The United States has enraged Russian officials by training the Georgian military, which has contributed 2,000 troops to American efforts in Iraq, and backing the country's application for membership to the North Atlantic Treaty Organization. Many Russians accuse Saakashvili of trying to seize Tskhinvali to quell the separatists in hopes of making Georgia more attractive for its NATO application.

The Kremlin sees the U.S. relationship with Georgia as part of a continued strategy to isolate it from the Soviet sphere of influence, including plans for a missile defense shield in Poland and the Czech Republic.

On Saturday morning, the Russian foreign ministry lashed out at Ukraine—another former Soviet republic that's applying for NATO membership with American support—for "vigorously arming the Georgian army to the teeth over the past few years, thus directly encouraging the Georgian leadership to invade South Ossetia."

Georgia is withdrawing its troops from Iraq as soon as transportation is arranged, which they've asked the United States to do, said Georgian commander Col. Bondo Maisuradze.

"We're ready to leave. We're just waiting for the plane now," Maisuradze said.

As of Saturday, flights to Georgia from Russia were canceled and access to its government Web sites from Moscow appeared to have been blocked.